Reorganize tests and benchmark scripts.

Mainly to get rid of one top level directory. But this will
also be useful when there are tests of the embedding API.

test/language/is/is.wren

@@ -0,0 +1,33 @@
+IO.print(Num is Class) // expect: true
+IO.print(true is Bool) // expect: true
+IO.print(new Fn { 1 } is Fn) // expect: true
+IO.print(123 is Num) // expect: true
+IO.print(null is Null) // expect: true
+IO.print("s" is String) // expect: true
+
+IO.print(Num is Bool) // expect: false
+IO.print(null is Class) // expect: false
+IO.print(true is Fn) // expect: false
+IO.print(new Fn { 1 } is Num) // expect: false
+IO.print("s" is Null) // expect: false
+IO.print(123 is String) // expect: false
+
+// Everything extends Object.
+IO.print(Num is Object) // expect: true
+IO.print(null is Object) // expect: true
+IO.print(true is Object) // expect: true
+IO.print(new Fn { 1 } is Object) // expect: true
+IO.print("s" is Object) // expect: true
+IO.print(123 is Object) // expect: true
+
+// Classes extend Class.
+IO.print(Num is Class) // expect: true
+IO.print(null is Class) // expect: false
+IO.print(true is Class) // expect: false
+IO.print(new Fn { 1 } is Class) // expect: false
+IO.print("s" is Class) // expect: false
+IO.print(123 is Class) // expect: false
+
+// Ignore newline after "is".
+IO.print(123 is
+  Num) // expect: true